Radiation imaging apparatus and method for breast

Abstract

A radiation imaging apparatus in which early recognition of breast cancer can be made possible by acquiring both a radiation tomographic image that accurately displays a tumor mass and a radiation planar image that accurately displays calcification. The apparatus includes an image processing unit for generating a tomographic image signal in a first imaging mode and generating a planar image signal in a second imaging mode, a computing unit for computing an imaging direction for obtaining a radiation planar image based on a location designated in a radiation tomographic image, and a control unit for controlling a rotational driving device and a radiation generating unit to obtain the radiation tomographic image in the first imaging mode, and controlling the rotational driving device according to the computed imaging direction and controlling the radiation generating unit to obtain the radiation planar image in the second imaging mode.

The invention claimed is: 
     
       1. A radiation imaging apparatus comprising:
 a table formed with an opening for allowing a breast of an examinee to pass through when the examinee lies down on the table; 
 a radiation generating unit for applying a radiation beam to the breast passing through the opening of said table; 
 a radiation detecting unit for detecting the radiation beam applied by said radiation generating unit and transmitted through the breast to output detection signal; 
 a supporting plate for supporting said radiation generating unit and said radiation detecting unit such that said radiation generating unit and said radiation detecting unit are rotatable around a rotational axis while facing each other with the breast in between, said rotational axis being substantially orthogonal to said table and passing through said opening; 
 a rotational driving device for rotating said supporting plate around the rotational axis; 
 an image processing unit for generating image signals representing a predetermined number of radiation images based on the detection signal outputted from said radiation detecting unit at each time when said radiation generating unit and said radiation detecting unit rotate by a predetermined angle and generating a tomographic image signal representing a radiation tomographic image by reconstructing the predetermined number of radiation images in a first imaging mode for obtaining the radiation tomographic image, and for generating a planar image signal representing a radiation planar image based on the detection signal outputted from said radiation detecting unit in a second imaging mode for obtaining the radiation planar image; 
 a computing unit for computing an imaging direction for obtaining the radiation planar image in the second imaging mode such that the imaging direction is substantially orthogonal to a plane including said rotational axis and a location designated in the radiation tomographic image obtained in the first imaging mode; 
 a control unit for controlling said rotational driving device and said radiation generating unit to perform imaging at each time when said radiation generating unit and said radiation detecting unit rotate by the predetermined angle so as to obtain the radiation tomographic image in the first imaging mode, and controlling said rotational driving device and said radiation generating unit to perform imaging in the imaging direction computed by said computing unit so as to obtain the radiation planar image in the second imaging mode; and 
 an image display unit for selectively displaying at least one of the radiation tomographic image obtained in the first imaging mode and the radiation planar image obtained in the second imaging mode. 
 
     
     
       2. The radiation imaging apparatus according to  claim 1 , further comprising:
 a pair of compression plates for compressing the breast passing through the opening of said table from both sides in the second imaging mode. 
 
     
     
       3. The radiation imaging apparatus according to  claim 2 , further comprising:
 a compression plate control unit for adjusting positions and directions of said pair of compression plates; 
 wherein said control unit controls said compression plate control unit such that said pair of compression plates are retracted from an imaging region between said radiation generating unit and said radiation detecting unit in the first imaging mode, and controls said compression plate control unit such that said pair of compression plates compress the breast from both sides along the imaging direction in the second imaging mode. 
 
     
     
       4. The radiation imaging apparatus according to  claim 1 , wherein said control unit sets a radiation dose to be used in the second imaging mode higher than that used in the first mode. 
     
     
       5. The radiation imaging apparatus according to  claim 1 , wherein said control unit changes at least one of a wavelength and a dose of radiation by changing at least one of a tubular voltage, a target, and a filter of said radiation generating unit to be used in the second imaging mode from that used in the first imaging mode. 
     
     
       6. The radiation imaging apparatus according to  claim 1 , wherein said control unit sets pixel density of said radiation detecting unit to be used in the second imaging mode higher than that used in the first imaging mode. 
     
     
       7. A radiation imaging method to be used in a radiation imaging apparatus including a table formed with an opening for allowing a breast of an examinee to pass through when the examinee lies down on the table, a radiation generating unit for applying a radiation beam to the breast passing through the opening of said table, a radiation detecting unit for detecting the radiation beam applied by said radiation generating unit and transmitted through the breast to output detection signal, a supporting plate for supporting said radiation generating unit and said radiation detecting unit such that said radiation generating unit and said radiation detecting unit are rotatable around a rotational axis while facing the breast in between, said rotational axis being substantially orthogonal to said table and passing through said opening, and a rotational driving device for rotating said supporting plate around the rotational axis, said method comprising the steps of:
 (a) controlling said rotational driving device and said radiation generating unit to perform imaging at each time when said radiation generating unit and said radiation detecting unit rotate by a predetermined angle so as to obtain a radiation tomographic image; 
 (b) generating image signals representing a predetermined number of radiation images based on the detection signal outputted from said radiation detecting unit at each time when said radiation generating unit and said radiation detecting unit rotate by the predetermined angle, and generating a tomographic image signal representing a radiation tomographic image by reconstructing the predetermined number of radiation images; 
 (c) computing an imaging direction for obtaining a radiation planar image such that the imaging direction is substantially orthogonal to a plane including said rotational axis and a location designated in the radiation tomographic image obtained at step (b); 
 (d) controlling said rotational driving device and said radiation generating unit to perform imaging in the imaging direction computed at step (c) so as to obtain the radiation planar image; 
 (e) generating a planar image signal representing the radiation planar image based on the detection signal outputted from said radiation detecting unit; and 
 (f) selectively displaying at least one of the radiation tomographic image obtained at step (b) and the radiation planar image obtained at step (e). 
 
     
     
       8. The radiation imaging method according to  claim 7 , wherein:
 step (a) includes controlling a compression plate control unit such that a pair of compression plates are retracted from an imaging region between said radiation generating unit and said radiation detecting unit; and 
 step (d) includes controlling said compression plate control unit such that said pair of compression plates compress the breast from both sides along the imaging direction. 
 
     
     
       9. The radiation imaging method according to  claim 7 , wherein step (d) includes setting a radiation dose to be used larger than that used at step (a). 
     
     
       10. The radiation imaging method according to  claim 7 , wherein step (d) includes changing at least one of a wavelength and a dose of radiation by changing at least one of a tubular voltage, a target, and a filter to be used from that used at step (a). 
     
     
       11. The radiation imaging method according to  claim 7 , wherein step (d) includes setting pixel density of said radiation detecting unit to be used higher than that used at step (a).